1) Field of the Invention
The present invention refers to a storage, homogenisation and dosing system, able to be used for substances that can precipitate or aggregate, such as in particular dying substances in liquid solution or solid.
2) Description of Related Art
The dying substances dosed individually in suitable proportions combine to prepare final dyes, which are then used in many fields of application.
The dying substances comprise organic or inorganic pigments, which can be used directly in solid form or else can be dispersed, in water or in other solvents, before use.
In the case of dying substances used in liquid form, these are previously stored in tanks that, through a hydraulic circuit, feed a system for dosing them. In automatic dosing of dying substances in whatever field of application, the end dying result is heavily influenced by the concentration of the raw materials used.
Therefore, the precision of the weight or volume measurements is obviously of fundamental importance for correct dosing of the dying substances, but, it is equally important to keep as perfect as possible homogeneity of the dying substances themselves.
In the case of dying substances mixed with one or more solvents or vehicles, due to phenomena of stratification and sedimentation, the solid particles, being heavier than the vehicle than the vehicle in which they are suspended, are bound by the force of gravity to sediment towards the lowest point of the plant, i.e. typically towards the bottom of the tank and along the vertical portions of the supply pipes of the product to the dosing system, up to the inside of the dosing valves.
Therefore, in the absence of suitable provisions, the lowest parts of the plant tend to build up more concentrated raw materials with respect to the upper areas.
In the best-case scenario, this leads to the manipulation, perhaps extremely precise, of portions of dying substances having a concentration that is variable in time.
At the start of the process a sufficiently homogeneous dying substance is picked up, whereas, as time passes and as phenomena of sedimentation occur, a dying substance richer in pigment (which have accumulated in the lower areas) is firstly picked up and then a dying substance impoverished by the same phenomenon is picked up.
The consequence is that, with an equal amount of dosed dying substance, the dying power, and therefore the tonalities resulting from their mixtures, are subject to variations out of all control.
In the worst-case scenario, the size of the phenomenon and the nature of the sedimented dying substance can cause the system to become blocked, as well as serious and irreversible damage to the plant.
To take into account this specific aspect, the solutions containing dying substances with solvents are added to with suitable surface-active chemical products, known as dispersants or suspending agents, which have a more or less strong stabilisation effect of the suspensions.
In order to further improve the situation, the viscosity of the dying materials tends to be increased, within the limits allowed by the subsequent use steps.
In both cases the problem is not solved in a radical and long-lasting manner, for which reason the builders of plants find themselves having to provide for a situation that is neither controlled nor standardisable.
To do this homogenisation systems are normally used based upon the use of agitators (to avoid phenomena of sedimentation inside the storage tanks) and of pumps and recycling circuits that are as long as possible (to avoid the phenomenon that also occurs inside the tubes and valves) and as powerful as possible (to avoid the load losses generated by the increase in viscosity of the raw materials and by the extension of the hydraulic delivery circuits for supply and return to the storage tank).
Some systems are equipped with slow anchor agitators at the moment placed in movement through a motor reducer. These systems allow the movement of the suspension inside the storage tank of the raw material.
A disadvantage is that their use is only possible in the case of almost continuous use, and therefore consequently involves substantial energy costs.
Moreover, these systems cannot be used in the case of very long feeding circuits.
Other systems are equipped with turboemulsifiers for highly viscous products that allow a substantial mass of highly viscous product to be used.
A disadvantage of these systems is that some particularly delicate dispersions can be irreversibly damaged by an excessive mechanical action.
Moreover, these systems also cannot be applied in the case of very long feeding circuits and in the case of non-continuous use. Other systems are equipped with complex hydraulic circuits with delivery and return lines and timed recycling pumps.
These systems allow optimal homogenisation inside the pipes and, with a series of provisions, also inside the storage tanks and the dosing valves.
A disadvantage of these systems is that they require greater costs, both in terms of energy needs, and in terms of time for the maintenance of the elements that make up the hydraulic circuit.
A disadvantage of the described systems is that they involve a substantial worsening of the costs represented, for example, by a greater value of the investment in the plant for double hydraulic circuits and/or for the assembly of the agitators.
Another disadvantage of all these systems is that they are complicated, given the increase in the number of dynamic components, such as pumps, agitators and integral recycling valves.
Another disadvantage is that the dynamic components, being subject to wear, require periodic maintenance, which is burdensome in terms of time and costs.
A further disadvantage of these systems is that they involve a considerable increase in the energy needs necessary for the operation of the plant.
Also in the case of dying substances or in any case reactants used directly in the solid form there can be problems of blocking of the system and damage to the plant caused by phenomena of aggregation of the solid particles in agglomerations, both inside the tanks and in other parts of the plant.
For this reason the tanks foresee kinematisms inside the tanks themselves capable of breaking the aggregations to keep the material finely dispersed.